Preparation of ketones



Oct. 13, 1964 w. J. PORTER ETAL 3,153,068

PREPARATION OF KETONES Filed July 6, 1960 FURNACE FEED s :2 CONDENSATION 9 7 REACTOR IO m I? I E SEPARATOR 3 l6 .WATER DRUM 23 n PRODUCT 'SPLITTER|5.\ DISTILLATION 2| l4 TOWER 22 HYDROGEN HYDROGENATlON 27 REACTOR 29 Walter Jome s Porter Edward Ben amin Ellerbe Inventors Patent Attorney United States Patent 3,153,068 PREPARATHGN 6F KETGNE Walter James Porter and Edward Benjamin Ellcrhe,

Baton Rouge, La, assignors to Esso Research and Engineering Qompany, a corporation of Delaware Filed July 6, 19%, Ser. No. 41,123 tllaims. (ill. 260-593) The present invention relates to a process for preparing ketones from oxygenated compounds. More particularly the invention concerns the use of unsupported catalyst particles in the conversion of low molecular weight alcohols and/or ketones, such as acetone and isopropanol, to high molecular weight ketones, such as mesityl oxide. Specifically, the invention involves carrying out the aforementioned conversion in the presence of a pilled or extruded catalyst comprising a Group ll metal oxide, e.g. zinc oxide, and an activator, e.g. zirconium oxide.

It is known in the art that acyclic alcohols can be dehydrogenated to make lretones that can be condensed at elevated temperatures to form ketone condensation products. For instance, isopropanol can be dehydrogenated to make acetone which condenses to form mesityl oxide, an unsaturated ketone. Mesityl oxide is readily hydrogenated in the presence of a suitable catalyst, such as nickel, at 140 to 270 F. under 1 to 25 atmospheres of hydrogen to produce methylisobutyl ketone (MIBK). The higher molecular weight ketones, especially MIBK and mesityl oxide, are useful as solvents for many organic substances, such as vinyl resins, polyacrylic esters and organic salt resins.

One difficulty which has been encountered in this process is the relatively low conversion of the lower molecular weight ketone to the higher molecular weight ketone in the reaction when supported catalysts, such as zinc oxide-zirconium oxide on coke, are used. Low conversion rates require separating large quantities of ketone feed from the product and recycling it to the reaction zone.

It has now been discovered that excellent selectivity and high conversions of lower molecular weight alcohols and/or ketones to higher ketones can be obtained by employing certain unsupported catalysts, i.e. extruded or pilled catalysts. Moreover, feeding hydrogen into the condensation reactor substantially increases the amount of higher ketone formed per pass. The catalyst employed in the present invention is a mixture consisting essentially of a major proportion of a Group II metal oxide and a minor proportion of thorium, cerium or Group IVB metal oxide (Periodic Chart of the Elements in Langes Handbook of Chemistry, 8th edition, pages 56- 57). One theory is that the thorium, cerium and Group IVB metal oxides behave as exciters or activators to stimulate the action of the Group ll metal oxides. There is no intention of limiting the invention to this theory, but rather it is intended to claim the use of the catalyst mixture, to be described hereinafter in more detail, in the process of the present invention.

, The accompanying drawing is a flow diagram of a preferred embodiment of the invention.

Incarrying out one embodiment of the invention, which can be a batch or continuous process, a vaporized feed comprising a low molecular weight saturated acyclic hydrocarbon lretone or alcohol preferably having a boiling point between about 120 and 185 F. is introduced into a reaction zone containing a pilled catalyst comprising from 1 to about 35 wt. percent of a. Group IVB metal oxide, such as zirconia or titania, and from 65 to 99 wt. percent of a Group llB metal oxide, such as zinc oxide. The feed should be preheated so that it enters the reaction zone in the form of a vapor at approximately the Patented Get. 13, 1964 reaction temperature. It has been found that the best results are obtained with a fixed catalyst bed in an isothermal or an adiabatic reactor (such as that described in US. Patent 2,835,706 issued to C. E. Cordes). The pressure in the reactor should be maintained at about 0.5 to 5 atmospheres and the temperature between about 300 and 700 F. While temperatures up to 900 F. may be employed, the catalyst activity is adversely affected at these temperatures due to the deposit of higher molecular weight by-products, such as isophorone, on the surface of the catalyst. The surprisingly high activity of the unsupported catalyst makes it possible to effect the condensation reaction at temperatures that are substantially below that required for supported catalysts without adversely affecting the product yield. The low reaction temperature reduces, and in some instances substantially elimi nates, catalyst fouling. Acliabatic reactors are preferred because they are simpler to operate and maintain, both echanically and processwise, than the typical isothermal reactors which have multiple tubes and direct firing. Moreover, they prevent the occurrence of hot spots which cause coke formation on the catalyst. The optimum conditions for effecting the condensation are temperatures of 500 to 600 or 700 F. and atmospheric pressure. It has been found that low feed partial pressures and/ or high velocities favor the reaction. While the space velocity is not critical, it is generally advantageous to pass the feed through the reaction zone at a space velocity based on liquid feed of 0.10 to 5 v./v./hr.

The catalyst particles are usually small, having an average diameter of between about to A2 inch. The particles may have a variety of shapes, such as cylindrical, round, cubical, etc. Their density should be at least 1.5 g./cc.

Increased yields of higher molecular weight keton product, both saturated and unsaturated, are obtained when hydrogen is introduced into the reaction zone either separately or admixed with the vaporized feed. It is particularly desirable to use hydrogen in combination with a catalyst containing more than 15 wt. percent activator. The amount of hydrogen introduced into the reaction zone should be carefully controlled. It has been found that when the molar ratio of hydrogen to ketone feed exceeds 3:1 the conversion to higher ketone is reduced. However, this may be offset by the increased life which accompanies the use of hydrogen. Where the feed is acetone, the greatest improvement in conversion is obtained with about 2 moles of hydrogen per mole of feed, although as little as 1 mole or as much as 4 or 5 moles of hydrogen has a pronounced effect on the catalyst life. The hydrogen not only results in the production Ofsignificant amounts of saturated ketone and improves catalyst life but it also significantly increases the yield 0 unsaturated ketone product, e.g. mesityl oxide.

While the solid catalyst particles may contain as little as 1 wt. percent activator, the finest catalysts for the process are those which contain more than 15 wt. percent activator, e.g. 16 to 30 wt. percent activator. The preferred catalysts are pellets consisting of to 84 wt. percent zinc oxide and 16 to 20 wt. percent zirconium oxide. Aside from zinc oxide, other metal oxides such as beryllium oxide and magnesium oxide, can be employed. -As mentioned above, other activators, such as titanium oxide, cerium oxide and thorium oxide, may be used in place of zirconium oxide.

Any suitable manner for preparing the catalyst may be employed, such as mixing and comminuting the two oxides in the proper proportions to form a homogeneous powder and then compacting or pressing the finely comminuted catalyst mixture into catalyst pellets of the desired shape. If the pellets do not have sufficient strength,

a small amount of binder, such as cement or clay may be added to the mixture prior to pressing it into pellets. For example, 1 to 15 parts by weight of a conventional catalyst binder may be admixed with 100 parts by weight of the catalyst before the catalyst is pilled. The surface area of the catalyst, which is usually about 1 to 4 sq. meters/g, may be substantially increased by admixing about 3 to 15 parts by weight of a combustible material, such as graphite, coke or other substance, and burning out the combustible material from the catalyst pellets. This may be accomplished by heating the catalyst in the presence of air or oxygen at high temperatures, e.g. about 1000" F. The catalyst may be pilled in any conventional press, such as a rotary press, or it may be extruded from an extrusion machine. If desired, the surface may be increased by crushing the catalyst particles until they are about to mesh (ca. to inch).

The catalyst pellets are more dense than the supported catalysts (2.5 times as dense as char base catalyst) and have a longer life. For instance, pilled catalysts can stay on stream for many months without regeneration, while supported catalysts have a relatively short life, i.e. about 1 month, and are sometimes diflicult to regenerate. The pilled catalyst can be regenerated by simply heating them to about 700 to 1200 F. in the presence of air to burn off contaminants.

The reaction products of the condensation step comprise mainly unsaturated higher molecular weight ketones, such as mesityl oxide, and minor amounts of saturated aliphatic and cyclic ketones, such as methylisobutyl ketone, phorone and isophorone. The conversion of a lower ketone to a higher molecular weight ketone with fresh catalyst pellets is generally greater than 10%, and at space velocities of 0.25 to 0.75 it may be as high as or Lower conversion rates, i.e. 12 to 15%, should be used where catalyst life is important.

While acetone is the preferred feed for this reaction, alcohols, especially isopropanol, and other oxygenated organic compounds, preferably saturated aliphatic compounds having 3 to 6 carbon atoms, such as methylethyl ketone, methylpropyl ketone and methylbutyl ketone, may be used to prepare higher unsaturated carbonyl compounds which can be hydrogenated to form ketones of increased molecular weight.

If an alcohol, such as isopropanol, is used as the feed, the first reaction is a dehydrogenation to make the corresponding ketone which is then condensed to form higher molecular weight ketones. When the pure acetone is fed into the reactor, some isopropanol is formed in the condensation zone. The formation of alcohol can be suppressed by introducing an equilibrium amount of isopropanol with the acetone feed. The suppression of alcohol formation favors the formation of the desired condensation product.

The reaction products of the condensation step, withdrawn from the reaction zone, are separated by any suitable technique such as fractional distillation. Any uncondensed feed, e.g. acetone, is recycled to the condensation reaction zone. The unsaturated ketone product, e.g. mesityl oxide, is then converted to saturated ketone product by introducing it into a hydrogenation zone which is at 140 to 270 F. and under 1 to 25 atmospheres of hydrogen pressure, hydrogenating the feed in the presence of a suitable hydrogenation catalyst, such as nickel, cobalt molybdate or copper chromite and recovering the saturated ketone, e.g. by distillation.

In the synthesis of -methylisobutyl ketone (MIBK) from acetone and/or isopropanol some methylisobutyl carbinol (MIBC) is formed in the hydrogenation step. Recycling the carbinol by-product to the hydrogenation reactor suppresses the formation of MIBC and in addition the recycled MIBC may act as a hydrogen donor.

The MIBC molecules that give up hydrogen will become MIBK.

In order to prevent runaway temperatures in the hydrogenation reactor and also obtain 100% conversion of the mesityl oxide formed in the condensation zone, the reactor is preferably operated on a feed that contains only a small amount of mesityl oxide, i.e. about 5 wt. percent. This is accomplished by blending about 1 part of fresh mesityl oxide feed with 19 parts by weight of the product from the reactor. Under these conditions the product contains little or no mesityl oxide which is difficult to separate from MIBK by distillation.

Referring now to the drawing, in a preferred embodiment of the invention a mixture of pure acetone and hydrogen (in a molal ration of 1 to 3) in line 5 is pumped through a furnace 6 to preheat the feed to 500 to 600 F. The preheated feed containing hydrogen is withdrawn from furnace 6 through line 7 and introduced into adiabatic condensation reactor 8, which is at approximately atmospheric pressure, at a space velocity of 0.25 to 0.75 v./v./hr. A substantial amount of the acetone in the feed is converted to mesityl oxide and MEBK. While the drawing shows only one reactor, a plurality of condensation reactors may be used. The reactor contains a fixed bed of catalyst pellets consisting of 16 to 20 wt. percent zirconium oxide and to 84 wt. percent zinc oxide. The reaction mixture is withdrawn from reactor 8 via line 9 and is cooled to about F. by cooling means 10 to condense most of the acetone, mesityl oxide and heavier products in the reaction mixture prior to introducing the mixture into the separation drum 11. The unreacted hydrogen gas is disengaged from the condensation products in drum 11 and re cycled to the feed line 5 via lines 12 and 13. The recycled hydrogen usually contains a small quantity, e.g. about 0.25 mole percent, of acetone. The liquid product in drum 11 is pumped into a splitter 14 through line 15 wherein acetone, isopropanol and water are separated from mesityl oxide and the heavier products. Splitter 14 is operated at about 180 F. and atmospheric pressure. The overhead product which contains acetone, isopropanol and water is withdrawn from splitter 14 through line 16 and introduced into a second splitter 17, which is also at atmospheric pressure and a somewhat lower temperature, to remove substantially all of the Water from the overhead stream. The water is withdrawn from the splitter 17 through line 18 and the almost water-free ketone and alcohol are recycled to feed line 5 through line 19. The mesityl oxide and heavier materials are withdrawn from the bottom of splitter 14 through line 20 and introduced into hydrogenation reactor 21 at space velocities of 0.1 to 20 v./v./hr. where it contacts hydrogen introduced into reactor 21 through line 22. The hydrogenation takes place in the liquid phase at about F. under about 10 atmospheres pressure in the presence of a nickel or other hydrogenation catalyst that favors the saturation of double bonds. The hydrogenation reactor is equipped with a heat exchanger means in order to withdraw the heat of reaction from the vessel. If desired, the mesityl oxide and MIBK withdrawn from the bottom of splitter 14 may first be split in a tower (not shown) to remove the heavier materials (mesitylene, phorone, and isophorone) before it is introduced into hydrogenation reactor 21. The unreacted hydrogen is withdrawn from hydrogen reactor 21 through line 23 and recycled to the hydrogen feed stream in line 22. The hydrogenated mesityl oxide is withdrawn from the bottom of reactor 21 through line 24 and introduced into distillation tower 25 which is operated at atmospheric pressure to separate the MIBK product from unreacted mesityl oxide, MIBC and other high boiling materials. Pure MIBK (99.5%) is withdrawn from distillation tower 25 overhead through line 26. The bottom product of distillation tower 25 is withdrawn through line 27 and a part or all of the bottoms product in line 27 may be recycled to the hydrogenation reactor via valve 28 and lines 29 and 20, or it may be recycled to feed line 5 via line 13. If the hydrogenated product in line 24 contains a significant amount of acetone and isopropanol, these substances may be removed in a stripper (not shown) prior to introducing the hydrogenated product into distillation tower 25.

The condensation step of the present invention is an improvement over the process described and claimed in US. Patent 2,549,508 which issued to Henry 0. Mottern on April 17, 1951. The present process is distlnguishable from the disclosures of the aforementioned patent in that it requires the use of a high density pelleted catalyst having a minimum dimension or diameter of at least inch. If particle sizes of less than inch are employed, the pressure drop across the bed will be unduly large and fines will cause clogging, etc. in the system. It has been found that when these minimum conditions are met higher yields of the condensation product and longer catalyst life are obtained. The density of the extruded or pressed catalyst pellets should be at least 1.5 g./cc., but preferably not more than 3 g./cc., since very high density catalyst pellets have little or no pores and therefore a low surface area. As mentioned above, in order to provide adequate contact between the catalyst and the reactants, the surface area should be at least 1 sq. meter/ g. and preferably is about 2 to 4 sq. meters/g. The surface area, of course, can be increased by crushing the pelleted catalyst or including a small amount of a combustible material, such as coke or a fatty acid, e.g. stearic acid, with the catalyst prior to forming the pellets and thereafter burning out the combustible material.

The following examples demonstrate how the process of the present invention may be carried out and its advantages over processes in which supported catalysts are used.

Example 1 A mixture consisting of 1 mole of acetone (99.5% pure) and 1 mole of hydrogen was preheated to 700 F. and continuously fed into an isothermal reactor that was at atmospheric pressure at a space velocity of 0.25 v./v./hr. The reactor contained a fixed bed of cylindrical catalyst pellets that were 8 to 14 mesh 7 to inch) consisting of 82 wt. percent zinc oxide activated with 18 wt. percent zirconium oxide (C.P. grade). The unsupported catalyst was prepared by pilling the zirconium oxide-zinc oxide mixture and then crushing the pills in a mortar and separating out the 8-14 mesh granules. It had a density of 2.25 g./cc. and a surface area of 2 sq. meters/ g. The conversion per single pass was 34.3% and the selectivities were as follows.

Selectivity,

Products: mole percent Mesityl oxide Methylisobutyl ketone 4 Mesitylene 9.5 Other ketones (phorone and isophorone) 20.5

When this same experiment was repeated with the exception that the catalyst was supported on char the conversion to mesityl oxide was only 19 wt. percent. From the foregoing it is evident that the use of pilled catalyst substantially improves the yield of mesityl oxide.

The catalyst used above was regenerated by air blowing it for 2 hours at 900 F. and steam treating it for 1 hour. The regenerated catalyst was compared under similar conditions with fresh and deactivated catalyst. The conversion data are given in the following table.

Acetone Catalyst: conversion, percent Fresh 34 Deactivated 21 Regenerated 31 The date of deactivation of the catalyst is substantially less than that of a supported catalyst, such as a char based catalyst. For instance, by maintaining the conversion at about 13%, a catalyst life of more than 4 months is obtained with the unsupported catalyst when operating at about 550 F. and a space velocity of 0.33 v./v./hr. under atmospheric pressure. An outstanding advantage of the process is that the catalyst permits the use of lower temperatures which, as mentioned above, also adds to catalyst life due to the reduction in deposits on the catalyst. By operating under optimum conditions, i.e. at about 550 to 700 F. and a space velocity of about 1 v./v./hr. conversions of 8 to 20% may be obtained for periods of up to 6 months without regeneration. The hydrogenation of mesityl oxide to MIBK is substantially quantitative. Generally the conversion of mesityl oxide is about 95% and the selectivity to MIBK is approximately 97%. Under the conditions in the foregoing preferred embodiment the selectivity to MIBC (methylisobutyl carbinol) is about 2%.

Example 2 The previous example is repeated using a feed mixture consisting of 1 mole of isopropanol and 1 mole of hydrogen.

It is not intended to restrict the present invention to the foregoing examples which are merely given to demonstrate some embodiments of the invention. It should only be limited to the appended claims in which it is intended to claim all of the novelty inherent in the invention as well as the modifications and equivalents coming within the scope and spirit of the invention.

What is claimed is:

l. A process for making higher molecular weight ketones which comprises contacting vapors of a C -C oxygenated, saturated, acyclic hydrocarbon feed selected from the group consisting of alcohols, ketones and mixtures thereof with a fixed bed of catalyst pellets having a density of at least 1.5 g./cc. and a surface area of at least 1 sq. meter/g, said catalyst pellets consisting essentially of about 70 to 99 wt. percent of an oxide of a metal selected from the group consisting of zinc, beryllium and magnesium and about 1 to 30 wt. percent of an oxide of a metal seletced from the group consisting of zirconium, titanium, cerium and thorium, at temperatures of about 300 to 700 F. and recovering higher molecular weight ketones from the resultant reaction products.

2. Process for making a higher molecular weight ketone which comprises contacting vapors of a C to C oxygenated, saturated, acyclic hydrocarbon feed selected from the group consisting of alcohols, ketones and mixtures thereof with a fixed bed of catalyst pellets having a density of at least 1.5 g./cc. and a surface area of at least 1 sq. m./g. and consisting essentially of about 70 to 99 wt. percent of an oxide of a metal selected from the group consisting of zinc, beryllium and magnesium and about 1 to 30 wt. percent of an oxide of a metal selected from the group consisting of zirconium, titanium, thorium and cerium in the presence of hydrogen in a reaction zone maintained at temperatures between 300 and 700 F. for a sufficient time to convert said feed to said higher molecular Weight ketone.

3. Process according to claim 2 in which the catalyst consists essentially of about 16 to 20 wt. percent zirconium oxide and about to 84 wt. percent zinc oxide.

4. Process according to claim 2 in which the oxygenated hydrocarbon is isopropanol and the higher molecular weight ketone is mesityl oxide.

5. Process according to claim 2 in which the oxygenated hydrocarbon is acetone and the higher molecular weight ketone is mesityl oxide.

6. Process according to claim 2 in which the oxygen ated hydrocarbon is a mixture of isopropanol and acetone and the higher molecular weight ketone is mesityl oxide.

7. Process for making higher molecular weight ketones which comprises introducing 1 mole of vaporized acetone at a space velocity of about 0.1 to 5 v./v./hr., and about 1 to 3 moles of hydrogen into an adiabatic reaction zone maintained at 500 to 700 F. and from about 0.5 to 5 atmospheres pressure containing a fixed bed of catalyst pellets consisting essentially of 16 to 20 wt. percent zirconium oxide and 80 to 84 wt. percent zinc oxide, said catalyst having a density of at least 1.5 g./cc. and a surface area of at least 1 sq. meter/g., contacting said acetone and hydrogen with said catalyst to convert acetone to higher molecular weight ketones, withdrawing reaction mixture from the reaction zone, separating higher molecular Weight ketones from the hydrogen and unreacted acetone and recycling said hydrogen and unreacted 15 acetone to the reaction zone.

10 oxide and 82 wt. percent oxide.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR MAKING HIGHER MOLECULAR WEIGHT KETONES WHICH COMPRISES CONTACTING VAPORS OF A C3-C6 OXYGENATED, SATURATED, ACYCLIC HYDROCARBON FEED SELECTED FROM THE GROUP CONSISTING OF ALCOHOLS, KETONES AND MIXTURES THEREOF WITH A FIXED BED OF CATALYST PELLETS HAVING A DENSITY OF AT LEST 1.5 G./CC. AND A SURFACE AREA OF AT LEAST 1 SQ. METER/G., SAID CATALYST PELLETS CONSISTING ESSENTIALLY OF ABOUT 70 TO 99 WT. PERCENT OF AN OXIDE OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZINC, BERYLLIUMAND MAGNESIUM AND ABOUT 1 TO 30 WT. PERCENT OF AN OXIDE OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM, TITANIUM, CERIUM AND THORIUM, AT TEMPERATURES OF ABOUT 300 TO 700*F. AND RECOVERING HIGHER MOLECULAR WEIGHT KETONES FROM THE RESULTANT REACTIN PRODUCTS. 